Helmets are worn to protect the head of the user from injuries that may occur in a wide variety of recreational, occupational, transportation, and military applications. The helmet design may vary depending on the type and frequency of expected impacts. Similarly, use patterns may vary from repeated removal of the helmet between short duration uses, such as those that may occur in football or hockey, to extended periods of use, such as those that may occur in occupational, transportation, or military applications, for example. In many applications, the helmet may extend partially or completely over the ears of the user. The helmet may be designed to reduce transmission of external sound, or to minimally impact transmission of external sound to the wearer. Active audio devices such as speakers and microphones and/or passive devices such as acoustic sound absorbing material may be used alone or in combination to provide the desired helmet acoustics.
In passive and active noise reduction helmet applications, performance and wear-ability may be improved by providing a complete seal around or within the ears without compromising comfort over long use durations. Current helmet designs appear to lack the ability to achieve these seal and comfort goals without significant tradeoffs between them.
A variety of non-military helmets and others that do not include fully customized shells provide adjustable ear cups. However, the ear cup assembly is mounted and positioned within the helmet using a repositionable or removable fastener, such as a hook and loop closure. The external shell is a hard molded shape with the ear cup assembly moveable within the inner lining of the shell. Foam pads and strips of hook and loop closure material is used to provide a customized fit for each user. These types of positioning systems require that the helmet be removed to position the ear cup assembly and comfortable positioning often requires several trial and error attempts by the user. These systems are also generally fixed or static once positioned within the helmet, although repeatedly wearing and removing the helmet may disturb the positioning of the ear cups. In addition, side pressure is established by the external shell dimension and the selection or combination of padding positioned through this iterative process. These systems are generally not amenable to additional adjustments during use with respect to position or pressure and may experience reduced performance with respect to comfort and seal over a particular period of use.
Helmets having active noise reduction (ANR) technology to cancel at least some of the unwanted external noise rely on a good seal around or in each ear to achieve best results. A good seal is particularly difficult to achieve inside a helmet for at least two reasons: helmets generally fit fairly tightly to provide their protective function, and the ear pinna protrudes from the surrounding surfaces of the head and varies in shapes and sizes among users. As such, putting the helmet on and proper positioning of previously placed ear cups or earphones can be very challenging. After the helmet is placed on the head, the seal around the ear may not be ideal based on ear position (within the ear cup) or the ear cup position relative to the skull. To achieve desired acoustic performance, users may over-compensate for acoustic leak paths by increasing the side pressure, which may result in reduced comfort particularly over long periods of time.
For best performance of an ANR system, the positioning of the ear canal and pinna relative to the driver/speaker and ANR feedback microphone within the ear cup or earphones should be understood and repeatable. Current solutions generally fail to deliver consistent performance with either the acoustics or the cushion/seal system. Available helmet shell-based solutions also generally do not offer customized left cup and right cup acoustic systems that are used by the best performing non-helmet based ANR headsets. Largely due to positioning and comfort constraints previously described, existing helmets use a full round/oval seal that does not leverage various advantages associated with a “slot seal” design that allows the pinna to extend into a slot between the cushion and other components of the ear cup, which may provide a better seal for a given amount of side pressure. This is likely because of the difficulty in positioning the pinna into the ear slot seal when donning the helmet due to the fixed ear cup within the helmet.